GB889924A - Improvements in or relating to electromagnetic brakes - Google Patents

Abstract

889,924. Electromagnetic brakes. DEWHURST & PARTNER Ltd., DEWHURST, M., and DEWHURST, A. Sept. 4, 1959, No. 30251/59. Class 103(1). In an electromagnetic brake, the energization of a winding causes the relative movement towards each other of two magnetic cores to control the brake through transmission means, the cores being releasably held in engagement with opposite sides of a pivot by spring means. Levers 1, 2 are pivoted to frame 10 at 7, 8, and carry shoes 4 which are biased against a drum 6 by a compression spring 9, Fig. 4, mounted between lever extensions 1a, 2a. The brake is released by energization of a winding 18 carried by a core 11 to attract a core 12, core 11 being prevented from rotation by a stop 23, 29; rotation of core 12 to abut core faces 11b, 12b moves a lever 25 to abut lever 1, and so move the levers 1, 2 apart. The cores 11, 12 are held in engagement with a pivot 13 on lever 2 by springs 14. The extent of lining wear and hence the gap between faces 11b, 12b is indicated by a pointer 36 pivotally mounted at 34 to core extension 11a and is engaged by an arm 37 pivoted at 35 to core extension 12a; a spring 26 connects pointer 36 to arm 37 which bears in a recess in a spring clip 38 mounted on pointer 36 (Fig. 3). When the brake is applied and the gap between faces 11b, 12b is correct, the pointer 36 is adjacent a mark 43 on a post 40; as the linings wear the pointer moves toward mark 42 since the rod 25 and head 24 rotate the core 12 relative to core 11. The gap is readjusted by moving a screw 28, abutting rod 25, into or out of lever 1. Initially, post 40 is set with faces 11b, 12b abutting and pointer 36 adjacent a mark 44; when the brake is applied the screw 28 is adjusted until the pointer is at 43. A window 45 in cover 27 enables the pointer to be seen. The compression of spring 9, Fig. 4, is adjusted by a screw 55 in extension 1a, which abuts a spring seat 51 fixed to a rod 48 slidable in extension 2a and supporting spring 9. An adjustable spring, Fig. 2, not shown, acts on extension 1a tending to release the brake to balance the bias on lever 2 due to the weight of the electromagnetic apparatus, thus ensuring that both shoes are applied. and released simultaneously. Specification 889,925 is referred to.